| The Japan Sea, a semi-enclosed marginal sea in the northwestern Pacific Ocean, is located between East Asia and the Japanese Island and connects with the East China Sea. It spans temperate and boreal climate zone, and are affected by warm Kuroshio Current (low latitude) and the polar atmospheric circulation (high latitude).In this study, we selected sediment grain size parameters, sediment geochemical elements of carbon and nitrogen, organic carbon and nitrogen isotope indicators, multi-core (LV53-4-1、LV53-15-3、LV53-17-2、lv53-19-3、lv53-26-2、LV53-27-2 LV53-30-1)and piston-core (LV53-23) samples from four region of the Japan Sea have been analyzed, based on the analysis of the above indexes suggesting sedimentary environment of the study area, the results are shown as follows:Five multi-core (LV53-4-1、LV53-15-3、LV53-17-2、LV53-27-2、LV53-30-1), which located in the north part、northwest and western slope and west seamounts of Japan Sea are mainly composed of silt and sand contents. It shows an increasing trend from the northeast part to southwest part, which may be associated with increasing hydrodynamic conditions.Proxies of TOC and TN from seven multi-core sediment indicate that, TOC and TN ranges 0.27%～2.92% and 0.02%～0.3%, respectively, displaying the same trend; Spatially, the total content of both TOC and TN descend from the northeast to the southwest of the Japan Sea, and high content of stations are found in the western side of the Japan Sea.C/N ratio、δ13C and δ15N from four multi-core all show that,the organic matter of three muilt-core (LV53-4-1、LV53-15-3、LV53-17-2),which close to the Eurasia,are dominated by the mixture of terrestrial and marine source. Terrigenous organic matter burial flux ranges from 0.11-0.28μg/(a*cm2), while LV53-19-3 located in the Yamato Ridge, far from land,the main source of organic matter is marine.It’s terrigenous organic matter burial flux ranges from 0.046～0.06μg/(a*cm2), and the relative contribution of terrigenous materials is 0.38.The 210Pb and particle size of sediments in four deep-water multicore sediments which are located in the middle, north and west of Japan Sea have been analyzed. The result shows that Yamato Ridge, northern part and western slope sediments of the Japan Sea are mainly silt and clayey silt for centuries. There is a significant biological disturbance phenomenon of surface sediments in the Yamato Ridge and the northern part of the Japan Sea, which does not exist in the western slope. The results of CRS and CFCS calculation show that, the modern average sedimentation rate of the Japan Sea is about 0.19-0.4 cm/yr, and the lowest value appears in the Yamato Ridge. The mean grainsize of four cores showed different patterns, but for the time interval of 1870-1940,1940-1980 and since 1980, the mean grainsize indicate that the sedimentary environment in the Japan Sea has undergone significant change, and this change is resulted from the super position of the deposition process at specific station on the regional climate and ocean environment background.Correlation of the dark layers found in the studied core by multi-proxy indicators and sediment description with the North hemisphere millennial scale climate changes and eustatic sea level fluctuations indicate that both an interstadial warming and sea level fluctuations influence on its formation, providing them an individual peculiarities. According to Marine Isotope Stage, LV53-23 from top to bottom was divided into three sections:A(0—42cm), B(42—138cm), C(138-200cm), corresponding to MIS1, MIS2 and MIS3. During MIS3 with sea level standing above-90 m, DL accumulation was associated with the interstadial warmings, increases in nutrient supplies to the Japan Sea and surface water productivity. During MIS 2 when sea level was nearly -90 m and sometimes below, sea level descending led to water column stratification and deficit in bottom water oxygenation resulted in organic enrichment in sediment and dark layers formation. During MIS 1, organic matter content showed a gradual decline trend, which may be related to the increase of the oxygen content in the bottom water and the preservation efficiency. |
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